title: Transformation of human mesenchymal stem cells in radiation carcinogenesis: long-term effect of ionizing radiation.
abstract: Increasing evidence on cancer stem cells suggest that stem cells are susceptive to carcinogenesis and consequently can be the origin of many cancers. We have recently established a telomerase-transduced human mesenchymal stem cell line and subsequently irradiated this in order to achieve malignant transformation. In the present study, we analyzed the long-term effect of ionizing radiation on these cells and investigate whether radiation can trigger tumor development. The cells were irradiated with a low (2.5 Gy) and a high (15 Gy) dose of gamma-rays and followed for up to 6 months after radiation. A subclone of the cells irradiated with 2.5 Gy of gamma-rays formed tumors after implantation to severe combined immunodeficiency mice. During the process of transformation, the cells showed accelerated telomere shortening, increased levels of anaphase bridges and a shift from balanced to unbalanced translocations. The tumor suppressor genes p53 and p21(CIP1) functioned normally throughout the study. Our observations indicate that radiation destabilized the telomeres and that the presence of uncapped telomeres initiated fusion-break-fusion cycles, resulting in increased chromosomal instability and tumor formation. Thus, bone marrow-derived human mesenchymal stem cells are capable of exhibiting a malignant phenotype.
authors.affiliation: Dept. of Human Genetics, University of Aarhus, Denmark.
authors.forename: Rikke
authors.initials: R
authors.lastname: Christensen
authors.forename: Jan
authors.initials: J
authors.lastname: Alsner
authors.forename: Flemming
authors.initials: F
authors.lastname: Brandt Sorensen
authors.forename: Frederik
authors.initials: F
authors.lastname: Dagnaes-Hansen
authors.forename: Steen
authors.initials: S
authors.lastname: Kolvraa
authors.forename: Nedime
authors.initials: N
authors.lastname: Serakinci
mesh_terms: D000705:Anaphase / Q000528:radiation effects; D000818:Animals; D001681:Biological Assay; D049109:Cell Proliferation / Q000528:radiation effects; D002471:Cell Transformation, Neoplastic / Q000528:radiation effects*; D016922:Cellular Senescence / Q000528:radiation effects; D002877:Chromosomes, Human / Q000378:metabolism; D016147:Genes, Tumor Suppressor; D006801:Humans; D007150:Immunohistochemistry; D059630:Mesenchymal Stem Cells / Q000201:enzymology / Q000378:metabolism / Q000473:pathology* / Q000528:radiation effects*; D051379:Mice; D009369:Neoplasms / Q000235:genetics / Q000473:pathology*; D009857:Oncogenes; D011839:Radiation, Ionizing; D019098:Telomerase / Q000378:metabolism; D016615:Telomere / Q000378:metabolism; D013997:Time Factors; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: C509186:TERT protein, human; D019098:Telomerase; D001616:beta-Galactosidase